Rotary drive anti-backlash device

ABSTRACT

A fuel delivery pump with a register having cost and volume counters for registering the cost and volume of each fuel delivery, separate rotary drive trains to the cost and volume counters, and an anti-backlash device associated with each rotary drive train to remove inertia overtravel of the counters upon termination of a fuel delivery. Each anti-backlash device comprises a drum and a helical coil spring surrounding the drum having a multiple-coil friction section with each helical coil in frictional engagement with the drum and a multiple-coil torsion spring section adapted to be torsionally loaded during the delivery of fuel and to rotate the rotary drive train backwards to remove any inertia overtravel at the termination of a fuel delivery.

. United States Patent [1 1 I Smilgys ROTARY DRIVE ANTl-BACKLASH DEVICE [75] Inventor: Bruno S. Smilgys, Hartford, Conn.

[73] Assignee: Veeder Industries llnc., Hartford,

Conn.

22 Filed: Jan.1l, 1974 1211 Appl. No; 432,577

[52] U.S. Cl. 235/131 R, 235/94 R [51] Int. Cl G06c 25/00 [58] Field of Search 235/94 A, 94 R, l3] R,

235/131 FD, 131 IA, 91 R [56] References Cited UNITED STATESPATENTS 5/1966 Pilz et a1. 235 131 R ll/l967 Sundblom 1. 235/94 A [111 3,847,347 14 1 Nov. 121, 1974 Primary ExaminerStephen J. Tomsky Attorney, Agent, or Firm'Prutzman, Hayes, Kalb & Chilton [57] ABSTRACT A fuel delivery pump with a register having cost and volume counters for registering the cost and volume of each fuel delivery, separate rotary drive trains to the cost and volume counters, and an anti-backlash device associated with each rotary drive train to remove iner- V tia overtravel of the counters upon termination of a fuel delivery. Each anti-backlash device comprises a drum and a helical coil spring surrounding the drum having a multiple-coil friction section with each helical coil in frictional engagement with the drum and a multiple-coil torsion spring section adapted to be torsionally loaded during the delivery of fuel and to rotate the rotary drive train backwards to remove any inertia overtravel at the termination of a fuel delivery.

9 Claims, 4 Drawing Figures 1 y ROTARY, nruvi; ANTI-BACKILASI-IIDEVICEI BRIEF DESCRIPTION OF THE INVENTION The present invention relates generally to rotary drive anti-backlash devices of the type shown and described in'U.S. Pat. No. 3,251,544, dated May 17, 1966 and entitled Gear'Train Control Arrangement,'and

more particularly to a new and improved rotary drive provided in the fuel delivery conduit has a rotary outusual cost and/or volume counters of the fuel pump register at the cessation ofa fuel delivery.-

It is another aim of the present invention to provide a new and improved rotary'drive anti-backlash device having an economical design and providing minimum resistance to the normal drive of the counter.

' It is a furtheraim of the present invention to provide pointed out more in detail hereinafter.

A- better understanding of the invention will be vob- I tained from the following detailed description and the accompanying drawing of illustrative applications of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a generally diagrammatic-front elevation view, partly broken away and partly in section, of a fuel delivery pump incorporating-a register with a pair of .rotary drive anti-backlash devices in accordance with the present invention; I

FIG. 2 is an enlarged partial side elevation view, partly broken away and partly in section, showing in part the rotary drive trains and rotary drive antibacklash devices of the fuel pump register;

FIG. 3 is an enlarged partial elevation view, partly broken away and partly in section, showing one of the rotary drive anti-backlash devices in more detail; and

DESCRIPTION OF THE PREFERREDv EMBODIMENTS Referring now to the drawing in detail wherein like reference numerals indicate like parts throughout the several figures, a fuel delivery pump 10 incorporating an embodiment of the present invention is shown having a nozzle 14 for delivery fuel and a suitable nozzle storage receptacle 15 for storing the nozzle 14 between fuel deliveries. Ina conventional manner, a meter 16 put shaft l7'driven in accordance. with the volume amount of fuel delivered. The meter shaft 17 is suitably coupled to a'rotary input or center shaft 18 of a varia- ;tor l9. Thevariator, 19 may, forexample,-be of the type described in US. Pat. No, 3,413,867 of Richard B. Hamlin, dated Dec. 3, 1968 and entitled Variator and employs settable gearing (not shown) which can be manually-set to establish the desired unit volume price of the fuel. The variator center shaft 18 extends through the variator and is connected via a rotary drive train for driving the usual pair of volume counters 22of a resettable register 24 of the fuel pump- 10 for registering the volume amount of fuel dispensed. A rotary outputgear 26 of the variator is driven by the meter 16 via the resettable variator gearing in accordance with the established unit volume price and is connected via a rotary drive train 34 for driving the usual pair of cost counters 28 of the register 24 for registering the cost amount of fuel dispensed in accordance with the unit volume price established by the setting of the variator 19.

The resettable register 24 may, for example, be of the type shown in US. 'PatpNo. 2,814,444 of Harvey N. Bliss, dated Nov. 26, 1957 and entitled Register and is-operable by a control handle 32 positioned adjacent the storage receptacle 15 such that the handle 32 has tobe rotated to itsvertical or off? position to permit the nozzle to be placed in its storage receptacle at the 24 is alsoconnected to a known manner to provide for de-energizing'a motor 36 for the usual fuel pump 38 when the handle32 is turned to its off position and for re-energizing the motor 36 after the volume and cost counters 22, 28 of the register 24 have been reset and their rotary drive trains have been re-engaged.

Referring specifically to FIGS. 2 and 3, the register drive train 34 to the cost counters 28 comprises a horizontal main or center shaft 40 driven by suitable bevel gearing 41, 42 from a vertical shaft 43 driven by the variator output gear 26 (FIG. 1). Gears 44, 4S fixed to the center shaft 40 at opposite ends thereof are connected for driving the lowest order counter wheel gears 46 of the cost counters 28 via intermediate gears 48.

Thus, the single horizontal shaft 40 is connected for driving the pair of cost counters 28. In the same mannet, a lower horizontal main or center shaft 50 is driven by the variator shaft l8'and is connected to drive the pair of volume counters 22.

As indicated, the counters 22, 28 are resettable between deliveries and as will be seen upon reference to the aforementioned US. Pat. No. 2,814,444, the counters are temporarily disengaged from the lowest order counter wheel drive gears 46 by the register reset mechanism as a part of the register reset cycle that takes place when the control handle'32 is rotated to its on or horizontal position.

In accordance with the present invention, a drive anti-backlash device 60 is mounted in association with each of the rotary drive trains 34, 35 to thecost-and volume counters 28, .22 respectively. Each 'antibacklash-device 60 comprisesa drum 62 fixed to the respective center shaft 40 or 50 and a helical coil' spring 64 encirclingthe. drum 62.'The drum'62 has an integral end flange 66, and a retaining washer 68 is rotatably mounted on the opposite end of thedrum 62 and is held against outer axial movement by a radially extending pin 69 which also provides for affixing the drum 62 to the respective center shaft 40or 50.

The drum 62 has a first cylindrical friction drum section 70 adjacent the end flange 66 and'a second reducedcylindrical drum section 72 having a diameter cal coil spring 64 is mounted on the drum 62 intermediate of and contained between the end flange 66 and ret'aining washer 68. The helical coil spring has a first free end74 adjacent the flange 66 and a second tangentially extending end 76 engageable with a fixed post 80 as the drum 62 is rotated during the delivery. of fuel, in the counterclockwise direction as viewed in FlGL-Z. The helical coil spring has a first multiple-coil friction spring section 81 with a plurality ofcoils (for example, 7 or 8 coils) each surrounding andin frictional engageslightly less than the friction drum section 70. The heliamount of angular loading is dependent on the spring rate and the number of coils contained in the torsion spring section 82, I

Thus,- duringv the delivery of fuel, the-torsionally such inertia overtravel typically occurring-when the.

- fuel delivery is quickly terminated especially from a high delivery rate. More significantly, the reverse angument with thefriction'drum section of thedrum 62.

The helical .coil spring 64 also'has a second multiplecoil torsion spring section 82 (having, for example, approximately the same number of .coils as the friction spring section 81) closely surrounding but preferably out of engagement with the reduced drum section 72. The helical coil spring 64 "hasa normalorunstressed diameter slightly less than the diameter of the friction drum section .70 and also preferably slightlygreater than the. diameter of. the 'reduceddrum section 72.

:Thusfwhen mounted onthe drum'. l0 asdescribed',

each of the coils of the friction section 8l frictionally engages the friction drum 70ialong substantially its entire-length to frictionally resist'the normal rotation of the drum 62, infthe counterclockwise direction as viewed in FIG] 12..The torsion spring sec tion'82 surrounding the reduced'drum section 72 preferably re .mains substantially out'of engagement with the drum during rotation of the rotary drive train. Also, the helicalcoil spring 64 is preferablyformed of wire having a square "crossse'ction as shown in FIG. 3 andtpreferably so that the coils are in engagement in the unstressed counters are reset. or g e c A modified rotary drive anti-backlash device90. is

lar bias of theloaded torsion spring'section is effective through the large contact area between the friction coils and the friction drum section, toangularly return the rotary drive train in the reverse angular direction and remove any inertia overtravel of the rotary drive train when it occurs. In addition, the reverse angular bias provided by the torsion coil spring section 82 holds the rotary drive train in proper drive engagement and prevents any vibration or shock caused forward rotary movement of the rotarydrive trainIwhen the countersaredise'ngaged for being reset. Thus, after the counters are reset and upon the commencementof a fuel delivery, the-rotarydrive train is substantially free offplay in the. driving direction. I

The torsional loading .of thetorsion spring section 82 during normal rotation of the rotary drive train, which as. previously indicated is preferably about 90 in the fuel pump register application, is preferably substantiallygreater than the maximum potential inertia overtravel of the rotary drivetrain at thedru'm' 62 and such that there is sufficient remaining torsional bias, after removalof the inertia overtravel, to prevent forward rotary movement of the rotary drive train while the shown in FIG. 4. The anti-backlash device 90 is very similar to the anti-backlash devie 60.described, except- .ing that the drum 91 of the anti-backlash device 90 is or unloadedcondition of the coil spring, and also such.

that each coil of wire of the friction section 81 has a flat area of contact with the friction drum section 70.

The coil spring 64 is coiled to extend helically from its free end 74 in the sameangular direction as the direction of rotation of the respective center shaft 40 or 50, in the counterclockwise direction as viewed in FIG. 2, and such that its frictional engagement with the friction drum section effects very slight expansionof the friction spring section 81 to .reduce thefrictional resistance on the drum as the rotary drive train is driven by the meter 16 to index the counters. Prior to the point where such relative rotation between the friction spring and friction drum sections begins, the torsion spring section 82- will be torsionally loaded by the frictional resistance between the friction spring section V and the drum. In the fuel pump register application described, the torsion spring section 82 is preferably angularly loaded approximately before the torsional resistance of the loaded torsion spring section 82 is sufficient to restrain the friction spring section 81 from further rotation with the drum, it being seen that the nonrotatable and the helical coil spring 92 encircling the drum 91 rotates with the respective center shaft 40 or 50 during the delivery of fuel. For that purpose the drum 91 is rotatably mounted on the respective center shaft 40 or 50; the end flange 66 is formed wih a bifurcated radially extending projection receiving the fixed post 80; and the opposite end of the helical coil spring 92 is formed to extend through an opening 95 in a suitable collar 96 affixed to the respective center shaft 40 or 50. The helical coil spring 92 is formed so that the spring extends helically from itsfreeend 74 in the angular direction opposite the directionof rotation of the respective center shaft 40 or 50 and such that it extends helically from its free end in the same direction as the relative rotation of the drum to the spring'whereby the frictional resistance causes slight expansion of the friction spring section. Also while the coilspringis rotating during thedelivery of fuel, there will be a slight centrifugal force effect on the coil spring coils which will have the effect of slightly reducing its'frictional restraint on the rotary drive train without reducing the, torsional t loading of the torsion springsection 82 andits effectiveness in removing an inertia overtravel of the rotary drive train at the end of a fuel delivery.

Thus, the anti-backlash device of the present invention employs very few inexpensive parts, can be readily mounted in association with a rotary drive train, and yet removes all play in the rotary drive train in the driving direction. r

As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can bemade without departing from the teachings of the present invention.

l claim: a

1. In a fluid delivery register for a fluid deliverysystem having fluid delivery means selectively. operable forinitiating and terminating the delivery of fluid, a fluid meterfor metering the amount of fluid delivered, and a first rotary drive train driven by the meter for operating the register comprising a variator having a rotaryinput connected to and rotated by the meter in accordance with the volumeamountof fluid delivered, a rotary outputifor operating the registerand gear means interconnecting therotary input and output settable for establishing the'unit volume price of the fluid and for rotating the rotary output in accordance with the rotation of the rotary input and the established unit volume price; the register having at least one resettable rotary counter with a plurality of coaxial rotary counter wheels of ascending order, a second rotary drive train connecting the rotary output of the variator with the lowest order counter wheel of said' one counter. to rotate the counter for registering the cost amount of fluid delivered and disengageable for disengagingthe second rotary drive train from said one counter, reset-means operable between fluid deliveries for temporarily disengaging each rotary drive train of the register and for resetting the coaxial counter wheels of each resettable rotarycounter rotated thereby while the rotary drive train is disengaged, and counter drive anti-backlash means for removing inertia overtravel of each counter upon termination of. a fluid delivery, the improvement wherein the counter drive anti-backlash means comprises a friction device connected to said second rotary drive train and having a drum member with an external annular friction surface; a coil spring having a first free end and a second end member, a first helical friction spring section with a plurality of generally helical friction coils extending from the first end, each surrounding and in frictional engagement with said annular friction surface, and a second torsion spring section be tween the first helical friction spring sectionand said second end member, and means mounting the drum member and said second end member of the coil spring for rotation in one angular direction of the drum member relative to the coil spring by the second rotary drive train, the helical friction coils of the friction spring section extending generally helically around said annular friction surface from said first end thereof in said one angular direction whereby upon rotation of the second counter drive train during the delivery of fluid, the frictional engagement of each helical coil of the friction spring section with the friction surface assists in angularly deflecting and thereby torsionally loading the tor- 2. A fluid delivery register according to claim 1 wherein the mounting meansprovides for restraining said second end member of the coil spring against rotation in said one angular direction and for rotation of the drum member in said one angular direction by said second rotary drive train.

3. A fluid delivery register according to claim 1 wherein the mounting means provides for restraining the drum member against rotation in the opposite angular directionrto said one angular direction and for rotation of saidsecond end member of the spring in said opposite angular direction by the second rotary drive train.

4. A fluid delivery register according to claim 1 wherein the friction'and torsion spring sections of the spring are formed by a plurality of continuous helical coils.

5. A fluid delivery register according to claim 1 wherein the register comprises at least two of said resettable rotary counters, wherein said second rotary drive train of the register connects the rotary output of the variator with the lowest order counter wheels of each of said two resettable rotary counters to rotate the counters to register the cost amount of fluid delivered and disengageable for disengaging the second rotary drive train from each of said two resettable rotary counters, and wherein said friction device is connected to said second rotary drive train of the register for removing inertia overtravel of both of said two resettable rotary counters. r

6. A fluid deliver y register according to claim 1 wherein the register comprises a second said resettable rotary counter, a third rotary counterdrive train connecting the rotary input of the variator to said second resettable rotary counter for rotating said second counter for registering the volume amount of fluid delivered and disengageable for disengaging the third rotary drive trainfrom saidsecond counter, and wherein the counter drive anti-backlash means comprises a second said friction device connected to said third rotary drive train for removing inertia overtravel of the lowest order counter wheel of said second resettable rotary counter.

7. Ina rotary drive train having a rotary drive member, a rotary driven member, an intermediate rotary drive means interconnecting the rotary drive and driven members for rotating the rotary driven member in a first rotational direction thereof by rotation of the rotary drive member in a first rotational direction thereof, the rotary drive train having rotary backlash between the rotary drive and driven members, and drive anti-backlash means for removing angular overtravel of the driven member in said first rotational direction thereof, comprising a drum member with an annular friction surface; a coil spring having a first free end and a second end member, a first multiple-coil friction spring section extending from the first free end and having a plurality of axially spaced coaxial annular coils, each in coaxial frictional engagement along substantially the full length thereof with said annular friction surface, and a second torsion spring section between the friction spring section and the second end member, means mounting the drum member and second end member of the coil spring for relative rotation of the drum member withrespect to the coil spring in one angular direction by the rotary drive train, the friction spring section extending generally helically from saidfirst end in an angular direction whereby upon rotation of therotary drive train to rotate the driven member in said one angular direction the frictional engagement of the friction spring section coils with the annular friction surface angularly deflects and thereby torsionally loads thetorsion' spring section and-angularly-deflects the friction spring section in a direction tending to reduce itsfrictio'nal engagement with the annular friction surface: I

8. In a fluid 'delivery register for a fluid delivery system having fluid delivery means selectively operable for initiating and terminating the-delivery of fluid and a fluid meterfor metering the amount of fluid delivered; the register having at least one rotary counter with a plurality of coaxialrotary counter wheels of ascending order, a rotary drive train having a rotary drive member adapted to be operatively connected to and driven by the meter, a rotary drivenrnember connected to the lowest-order counter wheel of each saidcounter for" rotating each said counter for accumulating the amount of fluid'delivered, intermediate rotary drive means interconnecting the rotary drive and driven members'for rotating the rotary driven member in a first rotational direction thereof by rotation of the rotary drive member'by the meter in a first rotational direction thereof foraccumulating the amount of fluid delivered, the rotary drive train having rotary backlash between the rotary drive and driven members, and counter drive anti-backlash means for removing inertia overtravel of each said counter upon termination of a fluid delivery; the improvement wherein the counter drive anti-backlash means comprises a friction device connected to said' rotary drive train having a drum member with an annular'friction surface, a spring having a first free endand a second end, a first multiplecoil friction spring section extending axially from said first end and having a plurality of axially extending coaxial annular coils, each in coaxial frictional engagerotary driven member is rotated? in said first rotational direction thereof, the annularfriction'coils of the friction spring section extending generally helically from said first end thereof in an angular direction whereby upon rotation of the counter drive train by the meter during the delivery of fluid, the frictional engagement of each annular coil of the friction spring section with the annular friction surface assists in angularly deflecting and thereby torsionally loading the torsion spring section and angularly deflects the frictionspring section ina direction tending to reduce its frictional engagement with the annular friction surface.

9. In a rotary drive train having a rotary drive member, a rotarydriven member, an intermediate rotary drive means interconnecting the rotary drive and driven members for rotating the rotary driven member in a first rotational direction thereof by rotation of the rotary drive member in a first rotational direction thereof, the rotary drive train having rotary backlash between the rotary drive and driven members, and drive anti-backlash means for removing angular overtravel of the driven member in said first rotational direction thereof, comprising a drum member with an an nular friction surface; a spring having a first free end and a second end, a first multiple-coil friction spring section extending from the first free end and having a plurality of axially extending coaxial annular coils, each gular direction the frictional engagement of the friction ment with said annular friction surface, and a second torsion spring section between the first friction spring section and said second end, and means mounting the drum member and said second end of the coil spring for rotation in one angular direction of the drum member relative to the coil spring by the rotary drive train as the spring section coils with the annular friction surface angularly deflects and thereby torsionally loads'the torsion spring section and angularly deflects the friction spring section in a direction te'ndingto reduce its frictional engagement with t e annular frictionsurface; 

1. In a fluid delivery register for a fluid delivery system having fluid delivery means selectively operable for initiating and terminating the delivery of fluid, a fluid meter for metering the amount of fluid delivered, and a first rotary drive train driven by the meter for operating the register comprising a variator having a rotary input connected to and rotated by the meter in accordance with the volume amount of fluid delivered, a rotary output for operating the register and gear means interconnecting the rotary input and output settable for establishing the unit volume price of the fluid and for rotating the rotary output in accordance with the rotation of the rotary input and the established unit volume price; the register having at least one resettable rotary counter with a plurality of coaxial rotary counter wheels of ascending order, a second rotary drive train connecting the rotary output of the variator with the lowest order counter wheel of said one counter to rotate the counter for registering the cost amount of fluid delivered and disengageable for disengaging the second rotary drive train from said one counter, reset means operable between fluid deliveries for temporarily disengaging each rotary drive train of the register and for resetting the coaxial counter wheels of each resettable rotary counter rotated thereby while the rotary drive train is disengaged, and counter drive anti-backlash means for removing inertia overtravel of each counter upon termination of a fluid delivery, the improvement wherein the counter drive antibacklash means comprises a friction device connected to said second rotary drive train and having a drum member with an external annular friction surface; a coil spring having a first free end and a second end member, a first helical friction spring section with a plurality of generally helical friction coils extending from the first end, each surrounding and in frictional engagement with said annular friction surface, and a second torsion spring section between the first helical friction spring section and said second end member, and means mounting the drum member and said second end member of the coil spring for rotation in one angular direction of the drum member relative to the coil spring by the second rotary drive train, the helical friction coils of the friction spring section extending generally helically around said annular friction surface from said first end thereof in said one angular direction whereby upon rotation of the second counter drive train during the delivery of fluid, the frictional engagement of each helical coil of the friction spring section with the friction surface assists in angularly deflecting and thereby torsionally loading the torsion spring section and radially expands the friction spring section to reduce its frictional engagement with the annular friction surface.
 2. A fluid delivery register according to claim 1 wherein the mounting means provides for restraining said second end member of the coil spring against rotation in said one angular direction and for rotation of the drum member in said one angular direction by said second rotary drive train.
 3. A fluid delivery register according to claim 1 wherein the mounting means provides for restraining the drum member against rotation in the opposite angular direction to said one angular direction and for rotation of said second end member of the spring in said opposite angular direction by the second rotary drive train.
 4. A fluid delivery register according to claim 1 wherein the friction and torsion spring sections of the spring are formed by a plurality of continuous helical coils.
 5. A fluid delivery register according to claim 1 wherein the register comprises at least two of said resettable rotary counters, wherein said second rotary drive train of the register connects the rotary output of the variator with the lowest order counter wheels of each of said two resettable rotary counters to rotate the counters to register the cost amount of fluid delivered and disengageable for disengaging the second rotary drive train from each of said two resettable rotary counters, and wherein said friction device is connected to said second rotary drive train of the register for removing inertia overtravel of both of said two Resettable rotary counters.
 6. A fluid delivery register according to claim 1 wherein the register comprises a second said resettable rotary counter, a third rotary counter drive train connecting the rotary input of the variator to said second resettable rotary counter for rotating said second counter for registering the volume amount of fluid delivered and disengageable for disengaging the third rotary drive train from said second counter, and wherein the counter drive anti-backlash means comprises a second said friction device connected to said third rotary drive train for removing inertia overtravel of the lowest order counter wheel of said second resettable rotary counter.
 7. In a rotary drive train having a rotary drive member, a rotary driven member, an intermediate rotary drive means interconnecting the rotary drive and driven members for rotating the rotary driven member in a first rotational direction thereof by rotation of the rotary drive member in a first rotational direction thereof, the rotary drive train having rotary backlash between the rotary drive and driven members, and drive anti-backlash means for removing angular overtravel of the driven member in said first rotational direction thereof, comprising a drum member with an annular friction surface; a coil spring having a first free end and a second end member, a first multiple-coil friction spring section extending from the first free end and having a plurality of axially spaced coaxial annular coils, each in coaxial frictional engagement along substantially the full length thereof with said annular friction surface, and a second torsion spring section between the friction spring section and the second end member, means mounting the drum member and second end member of the coil spring for relative rotation of the drum member with respect to the coil spring in one angular direction by the rotary drive train, the friction spring section extending generally helically from said first end in an angular direction whereby upon rotation of the rotary drive train to rotate the driven member in said one angular direction the frictional engagement of the friction spring section coils with the annular friction surface angularly deflects and thereby torsionally loads the torsion spring section and angularly deflects the friction spring section in a direction tending to reduce its frictional engagement with the annular friction surface.
 8. In a fluid delivery register for a fluid delivery system having fluid delivery means selectively operable for initiating and terminating the delivery of fluid and a fluid meter for metering the amount of fluid delivered; the register having at least one rotary counter with a plurality of coaxial rotary counter wheels of ascending order, a rotary drive train having a rotary drive member adapted to be operatively connected to and driven by the meter, a rotary driven member connected to the lowest order counter wheel of each said counter for rotating each said counter for accumulating the amount of fluid delivered, intermediate rotary drive means interconnecting the rotary drive and driven members for rotating the rotary driven member in a first rotational direction thereof by rotation of the rotary drive member by the meter in a first rotational direction thereof for accumulating the amount of fluid delivered, the rotary drive train having rotary backlash between the rotary drive and driven members, and counter drive anti-backlash means for removing inertia overtravel of each said counter upon termination of a fluid delivery; the improvement wherein the counter drive anti-backlash means comprises a friction device connected to said rotary drive train having a drum member with an annular friction surface, a spring having a first free end and a second end, a first multiple-coil friction spring section extending axially from said first end and having a plurality of axially extending coaxial annular coils, each in coaxial frictional engagement with said annular friction surface, aNd a second torsion spring section between the first friction spring section and said second end, and means mounting the drum member and said second end of the coil spring for rotation in one angular direction of the drum member relative to the coil spring by the rotary drive train as the rotary driven member is rotated in said first rotational direction thereof, the annular friction coils of the friction spring section extending generally helically from said first end thereof in an angular direction whereby upon rotation of the counter drive train by the meter during the delivery of fluid, the frictional engagement of each annular coil of the friction spring section with the annular friction surface assists in angularly deflecting and thereby torsionally loading the torsion spring section and angularly deflects the friction spring section in a direction tending to reduce its frictional engagement with the annular friction surface.
 9. In a rotary drive train having a rotary drive member, a rotary driven member, an intermediate rotary drive means interconnecting the rotary drive and driven members for rotating the rotary driven member in a first rotational direction thereof by rotation of the rotary drive member in a first rotational direction thereof, the rotary drive train having rotary backlash between the rotary drive and driven members, and drive anti-backlash means for removing angular overtravel of the driven member in said first rotational direction thereof, comprising a drum member with an annular friction surface; a spring having a first free end and a second end, a first multiple-coil friction spring section extending from the first free end and having a plurality of axially extending coaxial annular coils, each in coaxial frictional engagement with said annular friction surface, and a second torsion spring section between the friction spring section and the second end, means mounting the drum member and second end of the spring for relative rotation of the drum member with respect to the spring in one angular direction by the rotary drive train, the friction spring section extending generally helically from said first end in an angular direction whereby upon rotation of the rotary drive train to rotate the driven member in said one angular direction the frictional engagement of the friction spring section coils with the annular friction surface angularly deflects and thereby torsionally loads the torsion spring section and angularly deflects the friction spring section in a direction tending to reduce its frictional engagement with the annular friction surface. 